Synchronous Subsampling Circuit for Precise Wheel Speed Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing measurement systems for aircraft wheel speeds, particularly those using variable-excitation sensors, face challenges in achieving high accuracy and reducing complexity and cost, especially when dealing with high excitation frequencies, due to the need for expensive and complex electronics and high processing power.
Innovation Solution
An electronic circuit that uses a synchronized excitation and sampling frequency generated from the same clock signal, employing a digital envelope detector with optimized subsampling and a synchronous demodulator to handle spectrum folding, allowing high accuracy without requiring fast and costly analog-to-digital converters or excessive processing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high excitation frequency is used to increase useful signal level, then measurement precision is improved, but device complexity and cost increase due to requirement for fast analog-to-digital converters operating at tens of megahertz
Solution Approach 1:
The patent applies periodic subsampling at a frequency lower than the excitation frequency, where the sampling is synchronized to the excitation period. By sampling at specific phases within each excitation cycle and accumulating samples over multiple periods, the system achieves accurate measurement without requiring high-speed converters. The periodic nature of the excitation and synchronized subsampling allows harmonic elimination through proper timing selection.
Solution Approach 2:
The patent introduces an intermediary processing stage that accumulates and averages multiple subsampled measurements over several excitation periods. This intermediate accumulation process acts as a mediator between the low-speed sampling and the high-frequency excitation, effectively filtering out high-frequency harmonics and noise while preserving the fundamental measurement signal, thereby reducing the speed requirements for the analog-to-digital converter.
2Measurement precision
If high excitation frequency is used to increase useful signal level, then measurement precision is improved, but processing power requirements increase
Solution Approach 1:
The system uses periodic subsampling synchronized to the excitation frequency, collecting a limited number of samples per excitation period over multiple periods. This periodic approach reduces the total number of samples that need to be processed compared to continuous high-speed sampling, thereby reducing computational load while maintaining measurement precision through coherent integration of samples.
Solution Approach 2:
The patent employs subsampling that deliberately samples at a rate below the Nyquist rate for the excitation frequency, relying on the periodic structure and synchronization to recover accurate measurements. This partial sampling approach processes fewer data points than full-rate sampling would require, reducing processing power needs while achieving the same measurement accuracy through intelligent sample selection and accumulation.
3Measurement precision
If oversampling is used to eliminate harmonics according to Shannon's theorem, then measurement precision is improved, but device complexity and processing power increase due to requirement for high sampling frequencies
Solution Approach 1:
Instead of continuous oversampling at high frequencies, the patent implements periodic subsampling synchronized to the excitation period. By strategically selecting sample phases within each period and accumulating over multiple periods, the system eliminates harmonics through coherent integration rather than through high sampling rate, thereby achieving the same harmonic rejection with much lower sampling frequency requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables high accuracy in measuring wheel speeds with reduced complexity and cost, achieving measurement errors of 0.0002° rms for angular position, which meets the required performance without the need for expensive components or increased processing demands.
Implementation Method 1
The transmitter winding 6 and the measurement windings 7 are connected to an electronic unit 10 that is incorporated in the axle 3 in this example. The electronic unit 10 generates an excitation signal and applies it to the transmitter winding 6. When the transmitter winding 6 is excited by the excitation signal, an induced signal appears in the receiver winding 8 and is then transmitted by the target windings 9 so as to generate a measurement signal in each measurement winding 7
Data Source
AI summary
An electronic circuit (12) connected to a variable-excitation sensor (24) and comprising:a digital envelope detector (20) arranged to acquire signal that is produced by the sensor in response to an excitation signal, the detector comprising:an analog-to-digital converter (22) arranged to sample the measurement signal in such a manner as to produce sample points during successive observation windows of duration T that comprise a number NS of sample points, the sample points being spaced apart by a sampling period TS, the sampling period TS and the duration T being such that:TS=NP·T0+(NT/NS)·T0 and T=NS·TS,where T0 is one excitation period of the excitation signal, where NP, NT, and NS are non-zero natural integers, and where NT is not a multiple of NS.